(a) Technical Field
The present invention relates to an apparatus and method for manufacturing a crash pad. More particularly, the present invention relates to an apparatus and method for manufacturing a crash pad, which can improve the productivity and decrease the costs for equipment and manufacturing by reducing the number of molds, the number of installation components and the number of processes and omitting the handwork, and can increase the degree of freedom of embossment design on the surface of a skin while overcoming an excessive loss due to a leakage of foaming liquid.
(b) Background Art
In general, crash pads are used as an interior material installed at front of driver and passenger seats to protect passengers at the time of collision between the passengers and the crash pad due to a vehicle accident. These crush pads are formed of foaming materials to achieve elastic cushion performance and impact absorbing characteristics to a certain degree while providing an aesthetically enhanced surface condition.
Crash pads for a vehicle usually include a skin which is a surface material that provides an enhanced aesthetic surface condition and a core that serves as a framework of the crash pad inside the skin. A foaming layer such as polypropylene (PP) foam and/or polyurethane (PU) foam is interposed between the skin and the core to provide cushioning performance and impact absorbing performance.
FIG. 1 is an exemplary view illustrating a process of manufacturing a typical crash pad. A core 1, a skin 2, and a foaming layer 3 are formed by a polymer injection molding method, a vacuum adsorption molding method and a foaming molding method, respectively, all processes of which will be described in detail with reference to FIG. 1 as follows.
First, a polymer resin material 1a is injected at a lower pressure into an injection mold including upper and lower molds 4 and 5 to form a core 1, and separately, the skin 2 that is preheated in a male type of vacuum forming mold 6 is inserted and molded by the vacuum adsorption method.
In particular, although not shown in the drawing, fine vacuum apertures for vacuum adsorbing the skin 2 in the vacuum forming mold 6 are formed in the vacuum forming mold 6, and the vacuum apertures are connected to one passageway in the mold and then connected to a large capacity of an external vacuum pump. Additionally, foaming liquid 3a is injected into the core 1 of lower mold 5, and then a forming upper mold 7 attached to the skin 2 is closed, compressing and joining the skin 2 attached to the upper mold 7 onto foaming liquid 3a of the lower mold 5.
Thereafter, an unnecessary edge portion (e.g., leakage portion of foaming liquid) of the skin 2 and the foaming layer 3 that are formed is cut and removed (e g, trimming), or the edge portion of the skin 2 is adhered and fixed to the core 1 by an adhesive such that the foaming layer 3 is covered.
However, this typical manufacturing method has limitations as follows.
First, since the core 1, the skin 2 and the foaming layer 3 need to be molded at separate molds, respectively, a total of three molds (e.g., core injection upper and lower mold, vacuum forming mold, and foaming upper mold) are required to manufacture the crash pad. Thus, there is a limitation in that the investment and manufacturing cost such as molding cost increase.
Furthermore, since the lower mold 5 and the foaming upper molding 7 is opened at the edge portion of a cavity even when in closed state, a leakage of foaming liquid may occur at the opened edge portion thus, causing an excessive loss of foaming liquid and an increase of the manufacturing cost.
As described in FIG. 1D, after the manufacturing, a separate process in which the edge portion of the skin 2 and the edge portion solidified due to the leakage of foaming liquid are separately cut or only a leakage portion is cut and then the edge portion of the skin 2 is covered and adhered by an adhesive is required to manufacture the crash pad. Additionally, since foaming liquid needs to be injected into the opened cavity (e.g., foaming cavity), there may be difficulty in accurately maintaining and controlling the injection temperature of foaming liquid within a regulated temperature range.
In addition, in a structure in which the foaming cavity is opened or foaming liquid is capable of leaking, the foaming layer 3 needs to be designed to have a substantially uniform thickness of about 5 mm or more due to early solidification of foaming liquid. This may be a cause of reducing the design degree of freedom of the crash pad (e g, limitation of open foaming).
In order to solve these limitations, a molding apparatus has been proposed that seals the foaming cavity by adhering the edge portion of the skin closely to the core using a slide mold while integrating the vacuum foaming mold and the foaming upper mold into one common mold. This provides a benefit of solving a limitation of an excessive loss of foaming liquid, and enables the improvement of the design degree of freedom of the crash pad.
FIG. 2 is an exemplary view illustrating a typical foaming integrated injection molding apparatus including a slide mold that prevents a leakage of foaming liquid. In an apparatus for manufacturing a crash pad, the crash pad may be manufactured by an In-Mold Grain (IMG) foaming integrated injection molding method. Specifically, the IMG foaming process refers to a method in which a skin is molded through skin heating and vacuum suctioning in a mold and simultaneously an embossment is formed on the surface of the skin by forming the embossment on the inner surface of the mold (e.g., vacuum forming mold) to form a skin (e.g., thermoplastic olefin (TOP) material).
As shown in the drawing, when the core injection molds 10 and 11 are combined, resin may be injected into the mold to form a core 1, and simultaneously, a skin 2 is formed by vacuum adsorption in a vacuum forming mold 12. Thereafter, the mold is rotated and transferred by an upper rotating unit to allow the vacuum forming mold 12 with the skin 2 to combine with the lower mold 11 with the core 1, and then foaming liquid is injected and foamed between the core 1 and the skin 2 to form a foaming layer 3.
When foaming liquid is injected, the slide mold 12a allows the edge portion of the skin 2 to adhere closely to the core 1 to seal a foaming cavity. In particular, the slide mold 12a moves forward by a predetermined distance for the sealing during the foaming, and then fixed to maintain the sealing. After the foaming, the slide mold 12a moves backward to eject a product.
As shown in FIG. 3, the sealing is performed while a sealing protrusion part 1c formed on core 1 is overlapped with the skin 2. Thus, preventing the foaming liquid from leaking by the sealing protrusion part 1c. 
This molding apparatus may substantially prevent a leakage of foaming liquid, and a part of molds are used in common, thereby reducing the number of molds, the mold cost, and the investment and manufacturing cost.
However, since an edge portion of the skin 2 is located under the slide mold 12a, the edge portion of the skin 2 needs to be cut separately, or an end finishing process (e.g., end wrapping process) of the skin 2 needs to be performed.
In a conventional crash pad manufacturing apparatus of the prior art, when the slide mold moves forward, the edge portion of the skin attached to a vacuum forming mold is bent toward the end of a core to allow the edge portion of the skin to adhere closely to the core. Thus, the foaming cavity may be entirely sealed by the edge portion of the skin adhering closely to the end of the core during the foaming process.
When foaming liquid is injected into the sealed forming cavity, a foaming layer may be formed in the sealed foaming cavity without a leakage of foaming liquid. Additionally, the skin end finishing process (e.g., end wrapping process) may be automatically performed while the edge portion of the skin bent by the slide mold is joined and fixed to the end portion of the foaming layer. Thus, a leakage of foaming liquid may be solved, and the cutting process or the wrapping process that has been manually performed may both be omitted. In addition, the productivity may be improved.
Moreover, according to another conventional molding apparatus, as shown in FIG. 2, since the vacuum adsorption molding of the skin is performed, apparatuses for the vacuum adsorption molding, i.e., an expensive mold with fine vacuum apertures, a vacuum pump for the material adsorption, and a heater for heating a material before the molding are required.
FIG. 4 is an exemplary view illustrating a heater and a vacuum pump together with a molding apparatus. As shown in FIG. 4, a vacuum pump 13 that applies a vacuum pressure to a vacuum aperture of a vacuum forming mold 12 and a heater 14 that heats a skin material 2a before the skin material 2a is adsorbed to the vacuum forming mold 12 are provided.
To manufacture a crash pad by an IMG foaming integrated injection molding method using the vacuum pump 13 and the heater 14, the vacuum forming mold 12 that forms a fine embossment on the skin material (e.g., TPO sheet) 2a without an embossment, particularly, an expensive nickel electroforming mold with fine vacuum apertures (e.g., fine apertures of 50 μm to 200 μm) formed throughout the inner surface of the mold to adsorb the skin material 2a to the inner surface of the mold are required. The heater 14 is needed to heat the skin material 2a before the mold adsorption, and a separate transfer device (not shown) that transfers the heated skin material 2a to the vacuum forming mold 12 are required.
In addition, the embossment may be formed on the surface of the skin only when the entire skin material can be adsorbed and fixed to the inner surface of the mold by applying a vacuum pressure via the vacuum aperture of the mold 12 and the material is strongly adsorbed to allow the surface portion of the skin material to be inserted into the embossment portion on the inner surface of the mold. Accordingly, a vacuum pressure that forms a strong suctioning force is required, and thus, a large capacity of vacuum pump and tank are required.
Finally, there is a limitation in that the equipment cost increases due to the installation of a nickel electroforming mold, a heater, a transfer device, and a large capacity of vacuum pump and tank.
Hereinafter, a limitation regarding the product quality will be described with reference to FIGS. 5 and 4. FIG. 5 is an exemplary cross-sectional view illustrating a skin during the vacuum forming, and FIG. 4 is an exemplary view of a part ‘A’.
FIG. 5 illustrates: (a) the skin material 2a heated by the heater and inserted into the mold 12; (b) molding performed while the skin material 2a is vacuum adsorbed to the inner surface of the mold by a vacuum suctioning force through a fine vacuum aperture of the mold 12; and (c) a state after the molding, which shows a typical limitation.
When a vacuum suctioning force is applied during the molding (b), the surface portion of the skin material 2a is inserted into the concave embossment on the inner surface of the mold, and then a convex embossment 2b is formed on the finally formed skin 2 as shown in FIG. 5. In particular, in the IMG embossment molding method using the vacuum adsorption, the quality deterioration may occur as shown in FIG. 5, which is caused by the shrinkage and rebounding of the embossment 2b of the skin 2 when the vacuum is released after the molding.
Additionally, to form the embossment 2b in the skin 2, the surface portion of the skin material 2a must be inserted into the embossment portion 12b on the inner surface of the mold 12 by the vacuum suctioning force. In this case, an excessive vacuum time is spent, and thus the productivity decreases.
Furthermore, in the vacuum adsorption method, it may be difficult to form a sharp portion and deal with an undercut portion. In addition, when trying to implement a stitch 2c on the surface of the skin 2, the stitch 2c is also formed by the embossment portion 12b in the inner surface of the mold 12. In particular, the stitch 2c is a portion of the skin surface that protrudes at a specific location, corresponding to the shape of the stitch on the surface of the skin 2.
Accordingly, as shown in FIG. 6, there is a limitation in that only a stitch having the same color as the skin 2 can be implemented and the realistic feeling of the stitch 2c is deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.